OBJECTIVES: To investigate the association between objectively measured sleep-disordered breathing (SDB) and cognitive impairment in community-dwelling older women and to determine whether the apolipoprotein E (APOE) ɛ4 allele modifies this association.
SETTING: Participants' homes and two sites of the Study of Osteoporotic Fractures (SOF).
PARTICIPANTS: Four hundred forty-eight women with a mean age±standard deviation (SD) of 82.8±3.4.
MEASUREMENTS: Participants completed the Mini-Mental State Examination (MMSE), Trail Making Test Part B (Trails B), and polysomnography (PSG). SDB indices were the apnea–hypopnea index (AHI), the central apnea index (CAI), and oxygen saturation (SaO2) nadir less than 80%. APOE ɛ4 was determined for a subset of 242 women. Cognitive impairment was defined as 1.5 SDs or more from the sample mean on either cognitive test (MMSE or Trails B).
RESULTS: All SDB indices were associated with cognitive impairment according to the MMSE (AHI (per SD, odds ratio (OR)=1.4, 95% confidence interval (CI)=1.03–1.9), AHI of ≥30 (OR=3.4, 95% CI=1.4–8.1), SaO2 nadir <80% (OR=2.7, 95% CI=1.1–6.6), and CAI (per SD, OR=1.4, 95% CI=1.1–1.7)). Weaker, nonsignificant associations emerged between SDB and Trails B. In women who completed genotyping, each SD increase in AHI was associated with 70% greater odds of cognitive impairment according to the MMSE (OR=1.7, 95% CI=1.2–2.6). Women with the ɛ4 allele had a nearly five times greater odds of impairment (per SD, OR=4.6, 95% CI-1.0–20.7); the association was smaller and nonsignificant in women without the ɛ4 allele (per SD, OR=1.5, 95% CI-0.9–2.4; P for interaction=.08).
CONCLUSION: SDB is an important risk factor for cognitive impairment in older women, especially those with the APOE ɛ4 allele. Mechanisms linking these disorders need to be identified.